Fibrous sheet enhancement

ABSTRACT

A method and composition are disclosed for providing a two-part polymer binder additive for a fibrous sheet by improving both its strength and durability. The polymer binder comprises both the addition of a resin system and an anionic polymer which impart both increased strength and resistance to moisture and sagging. The resin system includes a polyamidoamine-epihalohydrin resin, a latex and an anionic polymer.

[0001] This application claims the priority of U.S. provisionalapplication Serial No. 60/223,251, filed Aug. 4, 2000.

FIELD OF INVENTION

[0002] The present invention generally relates to fibrous sheets andmore specifically to polymer additives for fibrous sheets.

BACKGROUND

[0003] Fibrous sheets are used for a variety of different purposes andare comprised of an array of different fibers, binders and fillers. Forexample, fibrous sheets can be used as acoustical ceiling tiles, paperproducts and furniture board. Primarily, fibrous sheets are comprised ofmineral wool, perlite, cellulosic fibers, fillers and binders.

[0004] Fibrous sheet production utilizes combinations of fibers,fillers, bulking agents, binders, water, surfactants and other additivesmixed into a slurry and processed into a fibrous sheet. Examples offibers used may include mineral fiber, fiberglass, and cellulosicmaterial. Mineral wool is a lightweight, vitreous, silica-based materialspun into a fibrous structure similar to fiberglass. Cellulosic materialis typically in the form of newsprint. Added fillers may includeexpanded perlite, clay, titanium dioxide and calcium carbonate. Expandedperlite reduces material density, and clay enhances fire resistance.Examples of binders used in the production of fibrous sheets includestarch, latex and reconstituted paper products, which link together andcreate a binding system, locking all ingredients into a structuralmatrix.

[0005] Organic binders, such as starch, are often the primary componentproviding structural adhesion for the fibrous sheet. Starch is often thepreferred organic binder because it is relatively inexpensive. Forexample, fibrous sheets containing newsprint, mineral wool and perliteare often bound together by starch. Starch imparts both strength anddurability to the fibrous sheet structure.

[0006] Unfortunately, there is a limit to how much starch can be addedbefore the organic binder's properties begin to decline. Starch ishighly water-soluble and, when partially hydrolyzed, loses a portion ofits ability to bind the fibrous sheet components. Additionally,water-felted and cast panels tend to exhibit limited stability underhigh moisture loads given the hydrophilic nature of the cellulosicfibers. Furthermore, fibrous sheet strength and durability cannot simplybe enhanced by using increased quantities of starch and cellulose, sincestarch increases a fibrous sheet's susceptibility to moisture and sag.

[0007] Thus, a high degree of starch and cellulose can lead to saggingand weakening of the board. Also, fibrous sheets having large quantitiesof starch require elevated drying rates to remove excess water from theboard. Therefore, there is a need for a method for increasing both thestrength and durability of a fibrous sheet without the addition ofincreased quantities of starch. Additionally, there is a need for afibrous sheet that is not susceptible to sagging under high moistureloads and does not require increased drying times during processing.

SUMMARY

[0008] The present invention encompasses both a method and compositionfor providing a two-part polymer binder additive for a fibrous sheet forimproving both its strength and durability. The two-part polymer bindermay be added to augment current organic binders to increase suchdesirable board properties as strength and durability, or the polymersmay be added to reduce the amount of organic binder required.Additionally, the polymers may be added in place of conventional organicbinders or added to improve sag resistance in highly moist environments.

[0009] The two-part polymer binder comprises both the addition of aresin system and an anionic polymer which impart both increased strengthand resistance to moisture and sagging. The resin system comprises apolyamidoamine-epihalohydrin resin and a polymer having repeating unitsderived from an alkyl halide having at least one double bond and analkene.

[0010] In greater detail, the two-part polymer binder may be in a ratioof resin system to anionic polymer between about 0.1 to 1 and about 10to 1 by weight. Additionally, the alkyl halide may comprise an alkylhalide and the alkene may comprise an olefin or an ethylene.Furthermore, the anionic polymer may be a water soluble copolymer.

[0011] The method of forming an enhanced fibrous sheet includes thesteps of forming a fibrous slurry and mixing into the fibrous slurry aresin system. The resin system comprises a polyamidoamine-epihalohydrinresin and a polymer having repeating units derived from an alkyl halidehaving at least one double bond and an alkene. Next, added into the mixis an anionic polymer to form a flocculated mix, which is then formedinto a fibrous sheet. The fibrous sheet is then dried to form thefinished product.

[0012] Furthermore, the ratio of added resin system to anionic polymermay be between about 0.1 to 1 and 10 to 1 by weight. The resin systemmay be added to the formed fibrous slurry in an amount between about 2pounds to about 200 pounds per ton of fibrous slurry.

[0013] Additionally, a fibrous sheet is provided having at least onetype of fiber and an organic binder. The fibrous sheet also contains aresin system having a polyamidoamine-epihalohydrin resin and a polymerhaving repeating units derived from an alkyl halide having at least onedouble bond and an alkene. Furthermore, an anionic polymer is alsocontained within the fibrous sheet.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the drawings:

[0015]FIG. 1 is a graphical presentation of the plotted indentation dataof the control samples as compared to the samples containing theadditive polymers of the present invention;

[0016]FIG. 2 is a graphical presentation of the plotted compressiveyield strength data of the control samples as compared to the samplescontaining the additive polymers of the present invention;

[0017]FIG. 3 is a graphical presentation of the plotted modulus ofrupture (MOR) data of the control samples as compared to the samplescontaining the additive polymers of the present invention;

[0018]FIG. 4 is a graphical presentation of the plotted modulus ofelasticity (MOE) data of the control samples as compared to the samplescontaining the additive polymers of the present invention;

[0019]FIG. 5 is a graphical presentation of the plotted modulus ofrupture (MOR) data of a fiber board sample prepared using an inlineprocess run as opposed to a batch process containing the additivepolymers of the present invention; and

[0020]FIG. 6 is a graphical presentation of the plotted modulus ofelasticity (MOE) data of a fiber board sample prepared using an inlineprocess run as opposed to a batch process containing the additivepolymers of the present invention.

DETAILED DESCRIPTION

[0021] The present invention encompasses both a method and compositionfor providing a two-part polymer binder additive for a fibrous sheet byimproving both its strength and durability. The polymer binder comprisesboth the addition of a resin system and an anionic polymer which impartboth increased strength and resistance to moisture and sagging. Theresin system comprises a polyamidoamine-epihalohydrin resin and apolymer having repeating units derived from an alkyl halide having atleast one double bond and an alkene.

[0022] The resin system is essentially a polyamidoamine-epihalohydrinresin combined with a latex whereby the resin imparts a cationic chargeto the resin system. The fibrous slurry is commonly anionic and readilyassociates with the cationic resin system. The resin system preferablyprecedes the addition of the anionic polymer.

[0023] The anionic polymer is preferably added to the fibrous slurryafter the addition of the resin system. The polymer is preferably apolyacrylamide copolymer, such as HERCOBOND 2000® available fromHercules Incorporated of Wilmington, Del. The addition of the polymeradds a negative charge to the fibrous slurry and aids in the creation ofa complex, which imparts both durability and strength to the finishedfibrous sheet.

[0024] The ratio of resin system to anionic polymer added to the fibrousslurry by weight may be about 2:1. The ratio may be smaller or largerthan about 2:1, such as for example 0.1:1 or 10:1 by weight.Additionally, in one embodiment, the resin system is added to thefibrous slurry in an amount between about 2 pounds to about 200 poundsper ton of fibrous slurry. In an additional embodiment, the resin systemis added to the fibrous slurry in an amount between about 10 pounds toabout 60 pounds per ton of fibrous slurry.

[0025] Furthermore, the anionic polymer may be added to the fibrousslurry in an amount between about 0.2 pound to 100 pounds per ton offibrous slurry. In an additional embodiment, the anionic polymer may beadded to the fibrous slurry in an amount between about 1 pound to 8pounds per ton of fibrous slurry. Of course, even greater amounts may beadded to the slurry if the organic binder is to be replaced by orreduced by the added binders. Essentially, the upper limit on thequantity of binder added to the fibrous slurry is limited by economicfactors since most organic binders such as starch are relativelyinexpensive as compared to the polymer binders of the present invention.

[0026] The resin system comprises a mixture of apolyamidoamine-epihalohydrin and a component which cooperates with ormoderates its properties and may be selected from flexibilizingcomponents. Without wishing to be bound by any one theory, it isbelieved that the flexibilizing component functions to hindercrosslinking of the polyamidoamine-epihalohydrin. Such a resin system isdescribed in more detail in U.S. patent application Ser. No. ______[Attorney Docket No. P19657.S07] and is incorporated by reference asthough set forth in full within this application.

[0027] In greater detail, the polyamidoamine-epihalohydrin resin mayinclude polyamidoamine-epihalohydrin resins such as those disclosed inU.S. Pat. Nos. 2,926,116 and 2,926,154 to KEIM, incorporated byreference in their entirety herein. Polyamidoamine-epihalohydrin resinscan also be prepared in accordance with the teachings of U.S. Pat. No.5,614,597 to BOWER, commonly assigned to Hercules Incorporated, which isincorporated by reference in entirety herein. As discussed in U.S. Pat.No. 5,614,597 to BOWER, these processes typically involve reactingaqueous polyamidoamine with an excess of epihalohydrin to completelyconvert amine groups in the polyamidoamine to epihalohydrin adducts.During the reaction, halohydrin groups are added at the secondary aminegroups of the polyamidoamine.

[0028] After the epihalohydrin has been added and when heat evolutionhas subsided, the reaction mixture is heated to effect crosslinking andviscosity increase. During this reaction, azetidinium groups are formed.These functional groups are typically employed to impart wet strength topaper by forming a strong crosslinked network with the paper fibers.

[0029] Polyamidoamine-epihalohydrin resins for use includepolyamidoamine-epichlorohydrins such as those sold by HerculesIncorporated of Wilmington, Del., under various trade names. Preferredpolyamidoamine-epihalohydrin resins available from Hercules include theKYMENE® resins and the HERCOBOND® resins; KYMENE 557H® resin; KYMENE557LX® resin; KYMENE 557SLX® resin; KYMENE 557ULX® resin; KYMENE557ULX2® resin; KYMENE 709® resin; KYMENE 736® resin; and HERCOBOND5100® resin. Of these, KYMENE 557H® resin and HERCOBOND 5100® may beused as polyamidoamines, available in the form of aqueous solutions. Itis expressly contemplated that equivalents to each of the foregoingresins are within the scope of the present invention.

[0030] Materials for the flexibilizing component may include copolymersof alkyl halides and alkenes, such as copolymers of vinyl or alkylhalides and alkenes. Any alkyl halide and any alkene, which copolymerizeto form copolymers with each other, may be employed. Alkyl halides mayinclude alkyl and/or vinyl halides of from 2-12 C atoms, from 2-6 Catoms, from 2-4 C atoms and about 2 C atoms. Copolymers of vinyl halides(especially vinyl chloride) and alkenes, of from 2-12 C atoms, from 2-6C atoms, from 2-4 C atoms and of about 2-3 C atoms. Propylene and/orethylene may be used.

[0031] Copolymers of vinyl chloride and ethylene may be employed as theflexibilizing component. Exemplary copolymers of vinyl chloride andethylene are disclosed in U.S. Pat. No. 4,673,702 to IACOVIELLO, andU.S. Pat. No. 4,962,141 to IACOVIELLO, et al., incorporated by referencein their entireties herein. These copolymers (also referred to herein as“EVCl” copolymers) may be prepared in using any known method. By way ofexample, they may be prepared, for example in the form of an emulsion asdescribed in U.S. Pat. No. 4,962,141 to IACOVIELLO, et al.

[0032] Suitable EVCl copolymer emulsions may be prepared bycopolymerizing the monomers in the presence of suitable emulsifyingagents, such as protective colloids and surfactants, in an aqueousmedium under pressures generally not exceeding about 100 atm and in thepresence of a redox system which is added incrementally. Thecopolymerization reaction is performed under an ethylene pressure whichis sufficient to provide the copolymer with about 5 to 35 wt % ethylenecontent, preferably about 15 to 25 wt %. Pressures of about 50 to 100atm are generally used to afford such an ethylene content.

[0033] The EVCl copolymer emulsions may additionally contain from 0.1 to30 weight percent of an external crosslinking agent based upon the totalweight of the copolymer. Suitable external crosslinking agents includemelamine/formaldehyde resins, polyisocyanates such as water dispersiblepolymeric methyl diphenyl diisocyanates and water based phenolic resins.

[0034] In carrying out the polymerization, substantially all of thepolyvinyl alcohol and a portion of the vinyl chloride are initiallycharged into the polymerization vessel which is then pressured withethylene. At least about 5 wt % and preferably at least about 15 wt % ofthe total vinyl chloride to be polymerized is initially charged into thereactor. The remainder of the vinyl chloride is added after theinitially charged vinyl chloride monomer content has been substantiallyreduced. A controlled addition avoids over pressurization of thereactor. No more than 60% of the vinyl chloride should be chargedinitially since a prepolymer must be generated in-situ in order toobtain the desired stable emulsions.

[0035] The quantity of ethylene entering the copolymer is influenced bypressure, mixing, addition rate and the amount of free radicalgenerating source. The ethylene content of the polymer can be enhancedby increasing the ethylene pressure, increasing agitation and increasingthe free radical source rate.

[0036] The process of forming EVCl copolymer emulsions may comprisepreparing an aqueous solution containing a polyvinyl alcohol dispersingagent. The aqueous solution and initial charge of vinyl chloride may beadded to the polymerization vessel, and ethylene pressure may then beapplied to the desired value. The mixture is mixed thoroughly todissolve ethylene in the vinyl chloride and into the water phase. Thecharge can be conveniently elevated to polymerization temperature duringthis mixing period. A polymerization temperature of about 55° C. and anethylene pressure in the range of 750 psig to 1000 psig may be employedto provide a copolymer with about 20-30 wt % ethylene. Mixing can beeffected by means of an agitator or other known mechanism.

[0037] The polymerization is initiated by introducing initial amounts ofa free radical generating source into the reactor vessel containing themonomer premix. When employing a redox system, either the oxidant orreductant component can be added initially to the aqueous mediumcontaining the polyvinyl alcohol and vinyl chloride with the other redoxcomponent added to initiate the reaction. Upon initiating thepolymerization, any desired monomer such as the hydroxyalkyl- orcarboxylic acid-containing functional co-monomers disclosed herein maybe added incrementally to the reaction vessel.

[0038] The reaction may generally be continued until polymerization isno longer self-sustaining and desirably until the residual vinylchloride content is below 0.5%. The completed reaction product isremoved from the presence of ethylene and maintained at a temperatureabove the Tg of the copolymer while sealed from the atmosphere. Thereaction mixture can also be transferred to a degasser for removal ofunreacted ethylene.

[0039] One skilled in the art would appreciate that generically orspecifically defined reactants and conditions can be substituted byequivalent reactants and conditions. Especially preferred copolymers forthe flexibilizing component include those marketed by Air Products andChemicals, Inc., of Allentown, Pa., under the trade name AIRFLEX®;especially AIRFLEX 4530®. It is expressly contemplated that equivalentsto such vinyl chloride/ethylene copolymers are within the scope of thepresent invention.

[0040] Other materials for the flexibilizing component include FLEXBOND325® (vinyl acetate-acrylic copolymer latex), LUCIDENE 243®(styrene-acrylic polymer emulsion), HYCAR 26256® (acrylic estercopolymer latex) and MORKOTE 1725® (acrylic copolymer emulsion).Additionally, water compatible systems such as copolymers can containthe following monomers: methyl methacrylate, butyl acrylate, styrene,vinylidene chloride, acrylic acid, and methacrylic acid. Suitablecopolymers include acrylated urethanes prepared by reacting a hydroxyacrylate or methacrylate; a diol, polyester or diamine; and adiisocyanate can be used. Preferred monomers are disclosed in U.S. Pat.No. 5,716,603, which is hereby incorporated by reference as though setforth in full herein for its teachings in this regard. Other copolymersthat appear to be useful include acrylic and vinyl acrylic-basedmaterials.

[0041] The anionic component of the two-part polymer binder additive isan anionic polymer preferably added by weight in the ratio of one-partper two-parts resin system. The polymer can be any linear, branched orcrosslinked anionic polymer. The polymer may be a natural or syntheticpolymer. For example, the natural polymer may be carboxymethylcellulose(CMC), and the synthetic polymer may be a polymer or copolymer ofacrylic acid.

[0042] The anionic polymer is preferably water soluble and, by way ofexample, may be comprised of an acrylamide or acrylic polymer orcombinations thereof. The molecular weight of the anionic polymer is notcritical, but is preferred to be within a range of up to about 1million. Of course, the molecular weight can be greater than thepreferred range which is contemplated for use within the presenttwo-part polymer system. Polymers having a very low molecular weight areessentially limited only by economics, since more polymer must be addedto give a desired result.

[0043] In an embodiment, the anionic polymer may be a water solubleacrylamide terpolymer described in U.S. Pat. No. 5,543,446 andincorporated by reference as though set forth in full within thisapplication. The terpolymer comprises a (meth)acrylamide, anethylenically saturated, aliphatic carboxylic acid or salt and awater-soluble polyvinyl monomer. An example of such a terpolymer can beacrylamide/acrylic acid/methylene-bis-acrylamide having a molar ratio ofabout 92/8/0.018. As can be seen from this example, the water-solublepolyvinyl monomer component of the terpolymer comprises only a fractionof the terpolymer's total composition, thus copolymers of acrylamide andacrylic acid may also be used.

[0044] While not being bound to any one theory, it is believed that thetwo-part polymer binder forms a complex, which is crosslinked and formsa lattice work around the negatively charged fibers of the slurry sheetforming the board. The resin system is cationic, and the anionic polymeris anionic. The resin system may be added first to the fibrous slurrysince the slurry or fibrous component is negatively charged and isattracted to the positively charged resin system. The anionic polymer ispreferably added after the resin system as the negative charged drybinder can then bind and crosslink with the positively charged resinsystem to form a complex.

EXAMPLES

[0045] The invention will be more easily understood by referring to theexamples of the invention and the control examples that follow. Thefollowing examples are given for illustrative purposes and are not to beunderstood as limiting the present invention.

[0046] The modulus of rupture (MOR) of the board is measured by theprocedure given in ASTM D-1037. MOR is calculated as being equal to3PL/2bd² psi where:

[0047] P=peak force required to break the samples (lbs.)

[0048] L=span between the sample supports (inches)

[0049] b=width of the sample (inches)

[0050] d=thickness of the sample (inches)

[0051] MOR is corrected for density variations by multiplying by D²where D=desired density/actual density, wherein the desired density is1.40.

[0052] The modulus of elasticity (MOE) is essentially the measure offlexibility and can be determined using the equation below:${M\quad O\quad E} = {( \frac{1}{4} ) \cdot ( \frac{L}{t} )^{3} \cdot ( \frac{1}{w} ) \cdot ( \frac{F}{d} )}$

[0053] where:

[0054] MOE=Modulus of elasticity in flexure, [psi]

[0055] L=Length of test span, [in]

[0056] t=Thickness of the sample, [in]

[0057] w=Width of the sample, [in]${( \frac{F}{d} ) = {{Slope}\quad {of}\quad {the}\quad {force}\text{-}{deflection}\quad {curve}\quad {recorded}\quad {by}\quad {the}\quad {Instron}}},\lbrack {l\quad b\quad f\text{/}{in}} \rbrack$

[0058] The density of the board products set forth in the followingexamples is expressed in pounds per board foot (pfd) and is determinedby weighing a sample board having dimensions of one-foot square and athickness of one inch. The density calculation for thinner or thickerboards is computed by dividing the weight of a one-foot square boardsample by the thickness of the board sample expressed in inches.

[0059] The resin system component, known herein as Example A, can beprepared by adding 42.2 dry grams of KYMENE 557H wet strength resinavailable from Hercules Incorporated of Wilmington, Del., to 25 drygrams of Airflex 4530 available from Air Products and Chemicals, Inc. ofAllentown, Pa., with mechanical stirring. Next is added 62.5 grams ofdemineralized water to the mixture to yield a slightly blue opaque whitedispersion that is then stirred for about 15 minutes at roomtemperature.

[0060] The resin system component, known herein as Example B, can beprepared by adding 100 grams of Hercon® 70 sizing emulsion availablefrom Hercules Incorporated of Wilmington, Del., to 100 grams of ExampleA to yield an opaque white dispersion. The dispersion is then stirredfor about 15 minutes at room temperature. TABLE 1 Sample 1 2 3 4 5 6 7 89 10 Example A 2 4 6 8 10 (lbs/ton) Example B 2 4 6 8 10 (lbs/ton)Hercobond 2000 1 2 3 4  5 1 2 3 4  5 (lbs/ton)

[0061] Illustrated in Table 1 are ten sample handsheets prepared usingvarious formulations for representing fibrous sheet formulations. Fivesamples were prepared using Example A as the resin system component, andthe other five were prepared using Example B as the resin systemcomponent. Hercobond 2000®, a polyacrylamide copolymer, was added toeach handsheet formulation as the anionic polymer component. The resinsystem component and the anionic polymer component were added in theweight ratio of 2:1.

[0062] The raw materials comprising each of the handsheets includemineral wool, cellulose, broke (Scrap Board), clay (filler) and perlite.

[0063] The raw materials were added into a reactor vessel in the orderlisted above and mixed with water having a temperature between about 95°F. and about 110° F. After the addition of each material, theingredients were mixed for approximately one minute at a standard mixerspeed setting of 6 spd. Once the raw materials were mixed, the resinsystem component was added and mixed with the raw materials for about1-3minutes. After the addition of the resin system component, Hercobond2000® was added and mixed for about 1-3 minutes. A retention aid,Hercules 8102E, was also added and mixed for about 1-3 minutes after theaddition of the Hercobond 2000®.

[0064] The formed fibrous mix of raw materials and component polymerswas formed and pressed into a fibrous sheet of about 14 inches wide by26 inches in length. The fibrous sheet was first drained for about 25seconds and vacuum treated after about 15 seconds to a thickness ofabout ¾ inch. The sheet was then further pressed to a thickness of about½ inch on a porous plate with pressing conditions pressed to stops ofgreater than 7 tons and gauge pressure of 30 seconds. The sheet was thewrapped in foil and dried for about 1.25 hours at 375° F. and thenunwrapped and dried for about 2.25 hours at 375° F. The sheets werewrapped in foil to aid in the gelling of the starch under testconditions. Foil sheets are not required under typical production runsin an operational plant. The density of the finished handsheets rangedfrom between about 1.15 to about 1.25 pounds per board foot. TABLE 2Sample MOR (psi) MOE (ksi) Control 1 168.9 27.47 Control 2 173.4 28.33 1189.0 31.36 2 189.0 32.88 3 204.3 33.71 4 208.0 34.13 5 195.8 35.35 6185.6 30.85 7 180.8 30.94 8 187.9 31.38 9 188.3 31.90 10  190.3 33.94

[0065] Table 2 illustrates the modulus of elasticity (MOE) and themodulus of rupture (MOR) of the test sample handsheets, plus two controlsheets formed from the same components, except for the additive polymersof the present application. Table 2 highlights that the handsheetsformed with the additive polymers of the present application haveimproved MOE and MOR qualities as opposed to the control sheets formedwithout the additives. TABLE 3 Wet Tensile/ Amount of Additive (%) DryWet Dry Experi- Kymene Example Hercobond Tensile Tensile Tensile ment557H A 2000 (lb/in) (lb/in) (%)  1 0 0 0 25.6 0.7 3 (Con- trol)  2 0.5 00 27.8 6.9 25  3 1.0 0 0 29.5 8.5 29  4 0 1.0 0 30.4 7.5 25  5 1.0 0 0.531.3 10.0 32  6 0 1.0 0.5 29.4 7.8 27  7 0 0 0 19.4 0.4 2 (Con- trol)  80.5 0 0 22.2 4.2 19  9 1.0 0 0 23.5 4.3 18 10 0 1.0 0 24.1 4.8 20 11 1.00 0.5 25.4 5.4 21 12 0 1.0 0.5 24.5 4.8 20 13 0 3 1.5 48 12.0 25.0 14 06 3.0 60.0 16.5 27.5 15 0 6 1.0 50.0 10.5 21.0

[0066] Illustrated above in Table 3 are the experimental test resultsfor various cellulosic sheets of paper. The sample sheets were preparedby introducing one or more of the following polymer components: ExampleA, KYMENE® 557H and HERCOBOND® 2000 into the pulp mix. Additionally, twocontrol samples were produced which did not include the addition of theabove polymer components.

[0067] Samples 1 through 6 were prepared using a mixture of TownsendPaper unbleached kraft pulp and Stone Container double-lined kraft pulp(which was washed after repulping) in a ratio of about 3 to 1,respectively. Samples 7-12 were prepared using a mixture in a ratio ofabout 1 to 1 of Georgia Pacific St. Croix Northern Hardwood andGeorgianier J Softwood pulp.

[0068] The paper samples were prepared on the JACKSONVILLE PAPER MACHINE(a pilot paper machine) and refined to 408 cc CSF (“Canadian StandardFreeness”) for sample sheets 1-6 and 485 cc CSF for sample sheets 7-12.The dilution water had 25 pm alkalinity (NaHCO₃) and 50 pm hardness(CaCl₂).

[0069] The test samples were either prepared with Example A or KYMENE®557H. Additionally, HERCOBOND® 2000 was added to both the Example A andKYMENE® 557H containing samples. The test data illustrates that thetwo-part polymer formulation can be used to impart wet and dry strengthto paper. For example, the test data indicates that Example A, which isabout 63% KYMENE® 557H and 37% Airflex 4530, provides good wet strength,as measured by the ratio of wet tensile to dry tensile in experiments 4and 10 when compared with experiments 2, 3, 8 and 9. Additionally, whenHERCOBOND® 2000 is added, both wet and dry strength are improved asillustrated in experiments 5, 6, 11 and 12.

[0070] While Applicants have set forth embodiments as illustrated anddescribed above, it is recognized that variations may be made withrespect to disclosed embodiments. Therefore, while the invention hasbeen disclosed in various forms only, it will be obvious to thoseskilled in the art that many additions, deletions and modifications canbe made without departing from the spirit and scope of this invention,and no undue limits should be imposed except as set forth in thefollowing claims.

What is claimed is:
 1. A polymer binder for a fibrous sheet comprising:a resin system comprising a polyamidoamine-epihalohydrin resin and apolymer having repeating units derived from an alkyl halide having atleast one double bond and an alkene; and an anionic polymer.
 2. Thebinder of claim 1, wherein the ratio of resin system to anionic polymeris between about 0.1:1 to 10:1 by weight.
 3. The binder of claim 1,wherein the alkyl halide comprises a vinyl halide.
 4. The binder ofclaim 1, wherein the alkyl halide comprises a vinyl halide and thealkene comprises an olefin.
 5. The binder of claim 3, wherein the vinylhalide comprises vinyl chloride and the alkene comprises ethylene. 6.The binder of claim 1, wherein the alkyl halide comprises a vinyl halideand the alkene comprises ethylene.
 7. The binder of claim 1, wherein theanionic polymer is a water soluble copolymer.
 8. A method of forming afibrous sheet comprising: forming a fibrous slurry; mixing into thefibrous slurry a resin system comprised of apolyamidoamine-epihalohydrin resin and a polymer having repeating unitsderived from an alkyl halide having at least one double bond and analkene; next mixing into the fibrous slurry an anionic polymer; thenforming the fibrous slurry into a fibrous sheet; and drying the fibroussheet.
 9. The method of claim 8, wherein the ratio of added resin systemto anionic polymer is between about 0.1:1 to about 10:1 by weight. 10.The method of claim 8, wherein the resin system is added to the fibrousslurry in an amount between about 1 pound to about 200 pounds per tondry weight of fibrous slurry.
 11. The method of claim 8, wherein theresin system is added to the fibrous slurry between about 5 pounds perton to about 60 pounds per ton dry weight of fibrous slurry.
 12. Themethod of claim 8, wherein the anionic polymer is added to the fibrousslurry in an amount between about 0.2 pound to about 100 pounds per tondry weight of fibrous slurry.
 13. The method of claim 8, wherein theanionic polymer is added to the fibrous slurry in an amount betweenabout 2.5 pounds per ton to about 60 pounds per ton dry weight offibrous slurry.
 14. The method of claim 8, wherein the alkyl halidecomprises a vinyl halide.
 15. The method of claim 8, wherein the alkylhalide comprises a vinyl halide and the alkene comprises an olefin. 16.The method of claim 15, wherein the vinyl halide comprises vinylchloride and the alkene comprises ethylene.
 17. The method of claim 8,wherein the alkyl halide comprises a vinyl halide and the alkenecomprises ethylene.
 18. The method of claim 8, wherein the anionicpolymer is a polyacrylamide copolymer.
 19. A fibrous sheet comprising:at least one type of fiber; a resin system comprising apolyamidoamine-epihalohydrin resin and a polymer having repeating unitsderived from an alkyl halide having at least one double bond and analkene; and an anionic polymer.
 20. The fibrous sheet of claim 19,wherein the ratio of added resin system to anionic polymer is betweenabout 0.1:1 to about 10:1 by weight.
 21. The fibrous sheet of claim 19,wherein the fiber is selected from the group consisting of cellulose,mineral fiber, fiberglass, and combinations thereof.
 22. The fibroussheet of claim 19, further including an organic binder comprising astarch.
 23. The fibrous sheet of claim 19, further comprising a fillerselected from the group consisting of perlite, clay calcium carbonateand combinations thereof.
 24. The fibrous sheet of claim 19, wherein thealkyl halide comprises a vinyl halide and the alkene comprises ethylene.25. The fibrous sheet of claim 19, wherein the anionic polymer is awater soluble copolymer.